Math Problem Statement

find the circumcenter a(2,3) B(-4, -3) C(2,-3)

Solution

To find the circumcenter of a triangle, we follow these steps:

Steps:

  1. Circumcenter Definition:
    The circumcenter is the intersection of the perpendicular bisectors of the sides of a triangle.

  2. Midpoints of the Sides:
    Calculate the midpoints of two sides of the triangle.

  3. Slopes of the Sides:
    Determine the slopes of the chosen sides, then find the negative reciprocals to get the slopes of the perpendicular bisectors.

  4. Equations of the Perpendicular Bisectors:
    Use the midpoint and perpendicular slope to write the equations of the perpendicular bisectors.

  5. Intersection of the Perpendicular Bisectors:
    Solve the equations of the two perpendicular bisectors to find their intersection, which is the circumcenter.


Given Points:

  • A(2,3)A(2, 3), B(4,3)B(-4, -3), C(2,3)C(2, -3)

Step 1: Find the midpoints of two sides.

  • Midpoint of ABAB:
    MAB=(x1+x22,y1+y22)=(2+(4)2,3+(3)2)=(1,0)M_{AB} = \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right) = \left( \frac{2 + (-4)}{2}, \frac{3 + (-3)}{2} \right) = (-1, 0)

  • Midpoint of ACAC:
    MAC=(x1+x22,y1+y22)=(2+22,3+(3)2)=(2,0)M_{AC} = \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right) = \left( \frac{2 + 2}{2}, \frac{3 + (-3)}{2} \right) = (2, 0)


Step 2: Find the slopes of ABAB and ACAC.

  • Slope of ABAB:
    mAB=y2y1x2x1=3342=66=1m_{AB} = \frac{y_2 - y_1}{x_2 - x_1} = \frac{-3 - 3}{-4 - 2} = \frac{-6}{-6} = 1

  • Slope of ACAC:
    mAC=y2y1x2x1=3322=undefined (vertical line)m_{AC} = \frac{y_2 - y_1}{x_2 - x_1} = \frac{-3 - 3}{2 - 2} = \text{undefined (vertical line)}


Step 3: Find the slopes of the perpendicular bisectors.

  • Perpendicular slope of ABAB:
    The negative reciprocal of 11 is 1-1.

  • Perpendicular slope of ACAC:
    Since ACAC is vertical, its perpendicular slope is 00 (horizontal line).


Step 4: Equations of the perpendicular bisectors.

  • Perpendicular bisector of ABAB:
    Using point-slope form yy1=m(xx1)y - y_1 = m(x - x_1), with slope 1-1 and midpoint (1,0)(-1, 0):
    y0=1(x(1))    y=x1y - 0 = -1(x - (-1)) \implies y = -x - 1

  • Perpendicular bisector of ACAC:
    Using slope 00 and midpoint (2,0)(2, 0):
    y=0y = 0


Step 5: Solve for the intersection.

Solve the system of equations:

  1. y=x1y = -x - 1
  2. y=0y = 0

Substitute y=0y = 0 into y=x1y = -x - 1:
0=x1    x=10 = -x - 1 \implies x = -1

Thus, the circumcenter is:
(x,y)=(1,0)(x, y) = (-1, 0)


Final Answer:

The circumcenter is (1,0)(-1, 0).

Would you like a graphical representation or further details?


Related Questions for Practice:

  1. How is the circumcenter related to the circumcircle of a triangle?
  2. Can the circumcenter of a triangle lie outside the triangle? Why?
  3. How do you find the circumradius given the circumcenter?
  4. What is the circumcenter of a right triangle?
  5. How do you prove that the circumcenter is equidistant from all vertices of the triangle?

Tip: The circumcenter is always inside the triangle for acute triangles, on the hypotenuse for right triangles, and outside for obtuse triangles!

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Math Problem Analysis

Mathematical Concepts

Geometry
Coordinate Geometry
Circumcenter of a Triangle
Perpendicular Bisectors

Formulas

Midpoint formula: M = ((x1 + x2)/2, (y1 + y2)/2)
Slope formula: m = (y2 - y1) / (x2 - x1)
Point-slope form of a line: y - y1 = m(x - x1)

Theorems

A circumcenter is equidistant from all vertices of a triangle.
The circumcenter lies at the intersection of perpendicular bisectors of the sides of a triangle.

Suitable Grade Level

Grades 9-12